dc.contributor.advisor |
Taylor, Mark P. |
|
dc.contributor.advisor |
Metson, James B. |
|
dc.contributor.author |
Lavoie, Pascal |
|
dc.date.accessioned |
2021-06-23T21:47:41Z |
|
dc.date.available |
2021-06-23T21:47:41Z |
|
dc.date.issued |
2021 |
en |
dc.identifier.uri |
https://hdl.handle.net/2292/55394 |
|
dc.description.abstract |
Alumina dissolution in Hall-Héroult reduction cells is crucial to efficient and sustainable production of primary aluminium, an important structural light metals that has multiple applications in society. To meet the ever-growing demand for aluminium, reduction cells have increased in production intensity, which comes through either cell size increase (lenght) or increased amperage within an established design. As a result, the control of alumina dissolution is increasingly difficult. Multiple aspects of alumina dissolution had been studied, but mostly in laboratory. The understanding of the confluence between the laboratory findings and the industrial cell conditions was incomplete. The poor observability of the industrial feeding process itself certainly contributed to this knowledge gap. The central hypothesis contained in the present thesis is that by carefully controlling the sensible heat available within the feeding zone, the feeder hole can be maintained in a condition conducive to alumina dissolution. A novel and rigorous methodology was developed to study the links between the impact of the cell parameters on the feeder hole condition, and in turn the impact of the feeder hole condition on the dissolution and mixing behaviour of alumina within the cell. The research found that there are multiple pathways throughout the feeding sequence influencing the evolution of the feeder hole condition towards being either conducive to dissolution, or detrimental to it. The probabilities of following a given pathway are largely influenced by the initial feeder hole state and a few key cell parameters. Within the confines of this study, these parameters were determined to be the feed rate of a cell, its superheat, electrolyte chemistry (Excess AlF3 concentration), and the anode changing operation. The anode covering operation was also found to impact alumina concentration significantly, without finding long-term impacts. It was also found that very detrimental feeder hole conditions such as a blocked feeder hole, stems from abnormal assignable causes like very low liquid level or alumina leakage. Above this, it was found that the feeder hole condition is pivotal to ensure sustainability of dissolution behaviour throughout the feeding cycle. The feeder hole condition can be controlled by allowing the sensible heat in feeding zone to recover sufficiently between feed events. This is controlled primarily by feed rate, and is especially critical during the overfeed phase. The findings also demonstrate that there can be a temporary deterioration of feeder hole condition without necessarily impacting the long-term performance of the cell if the feeder hole condition recovers during underfeed before the subsequent overfeed phase. Finally, it was demonstrated that the cell performance is largely influenced by the ability to control dissolution. Changes made to the feed strategy to improve overall feeder hole condition resulted in substantial improvements of key performance outcome of the cells, namely current efficiency, energy consumption and anode effect frequency. |
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dc.publisher |
ResearchSpace@Auckland |
en |
dc.relation.ispartof |
PhD Thesis - University of Auckland |
en |
dc.relation.isreferencedby |
UoA99265344113302091 |
en |
dc.rights |
Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. |
en |
dc.rights |
Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. |
|
dc.rights.uri |
https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm |
en |
dc.rights.uri |
http://creativecommons.org/licenses/by-nc-sa/3.0/nz/ |
|
dc.title |
On the Factors Affecting Alumina Dissolution in Industrial Reduction Cells |
|
dc.type |
Thesis |
en |
thesis.degree.discipline |
Chemical and Materials Engineering |
|
thesis.degree.grantor |
The University of Auckland |
en |
thesis.degree.level |
Doctoral |
en |
thesis.degree.name |
PhD |
en |
dc.date.updated |
2021-06-23T01:21:56Z |
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dc.rights.holder |
Copyright: The author |
en |
dc.rights.accessrights |
http://purl.org/eprint/accessRights/OpenAccess |
en |
dc.identifier.wikidata |
Q112955838 |
|